Starting circuit for gaseous discharge lamps



Jan. 21, 1936. E, o, ERICKSON I 2,028,538

STARTING CIRCUIT FOR GASEOUS DISCHARGE LAMPS Filed Feb. 20, 1953 2 Sheets-Sheet 1 Jan. 21, 1936. E. o.- ERICKSON STARTING CIRCUIT FOR GASEOUS DISCHARGE L AMPS 2 Sheets-Sheet 2 Filed Feb. 20, 1953 Patented Jan. 21, 1936 U-NITIED STATES PATENT oFF ca STARTING CIRCUIT FOR GAS EOUS DISCHARGE LAMPS Ellis 0. Erickson, Pasadena, Calif., assignor to Claude Neon Electrical Products Corporation, Ltd., Wilmington, Del.,'a corporation of Delaware Application February 20, weasel-151 a. 657,486

' 9 Claims.

a. c. operated gaseous discharge lamps with relatively simple and inexpensive apparatus.

As .is well-known, gaseous discharge lamps usin mercury vapor, neon, or-other gases, are widely used, particularly for-advertising signs.

Many of these lamps are energized from transformers providing relatively high secondary potentials of several thousand volts. Because of the high potentials employed, these tubes start automatically as soonas the potential is applied, and no separate starting means is required. However, there have recently been developed gaseous discharge lamps having hot electron: emitting electrodes. as terminals, which tubes operate at relatively low potentialsin many instances less than l.,000 volts. Unfortunately, these lamps are not always capable of starting automatically in response to application of normal operating potential and; special startin existing across the tube te minals when the latter is functioning,- so that the initial ionization of the gasproduced by the spark coil does not always occur at a time when the normal potential, as delivered by the source of tube current across the tube terminals, is sufficient to sustain the discharge.

Throughout this description, wherever reference is made to the operating potential across the tube terminals. I mean the potential across the tube when the latter is functioning. This potential is less than and is out of phase with the open circuit potential ofthe transformer because of the resistance and leakage reactance of the transformer.

In accordance with the .present invention, I

shift the phase the potential applied to the spark coll by an amount and in a direction to. cause-the high frequency starting impulses pro tive ends of the tube and energized from low poduced thereby to occur substantially in phase with the normal operating potential across the tube terminals. There are several ways in which the f= desired phase shift may be obtained and some practical methods are disclosed in the following detailed description, which refers to the drawmgs.

In the drawings: Figure 1 is a schematic circuit diagram illus-" trating one method in accordance with my invention for starting a gaseous discharge tube from a source of single-phase alternating current.

Figure 2 is a diagram illustrating a modified form of the circuit shown in Figure 1. Figure 3 is a vector diagram illustrating the operation of the circuit shown in Figure 1. Figure 4 is a diagram containing curves illustrating the time ofoccurrence of the starting impulses relative to the times of maximum amplitude of the operating potential in a conventional circuit and in my circuit. s Figure 5 is a schematic circuit diagram illustrating a circuit in accordance with my invention, energized from ,a source of three-phase 26 alternating current.

Figure 6 is a vector diagram illustrating the I operation of the circuit shown in Figure 5.

Figure 7 is a curve showing the characteristics of the starting impulses produced by a spark coil-80 of a type employedfor starting gaseous discharge lamps. l Referring to the drawings, I have shown in Figure 1 a gaseous discharge tube l5 having a pair of 'hotcathodes l6 positioned at the respectential secondary windings ll of a transformer l8. The cathodes l6 are also connected to the respective opposite ends of a high potential secondary winding IS. The transformer I8 is provided with a; primary winding 20 which is shown connected through a switch 2H1. across a pair of 110-volt alternating current mains 2|.

In practice, the gaseous discharge tube I! may approximate ten feet in length, and may have an internal diameter of approximately one inch, under which condition the tube, after being once started, will operate very satisfactorily with the primary and secondary windings 20 and ll, respectively, of the transformer ",so proportioned as to deliver-a secondary potential of approxvide a spark coil 22, which is essentially a Tesla butis of greater magnitude. Theexact relative "coil comprising a secondary winding 25 of a great many turns, and a primary winding 24 of a few turnsv energized by the discharge from a condenser 50. The latter is connected in series with the winding 5| of a buzzer 52 across conductors 29 and 3| supplying energizing potential for the device. Buzzer contacts 53 make and-break the operating circuit of the buzzer winding El and .simultaneously discharge the condenser 50 through the primary winding 24 of the Teslacoil in a manner well-known in the art.

the buzzer vibrates during a portion of each halfcycle of the applied alternating current (while the amplitude of the a. c. wave is suihcient to pull the buzzer armature away from its contact) to produce a series of trains of high frequency impulses at half cycle intervals. The envelope of each train is of the general shape shown in curves 34 and in Figure 4, and, as shown in Figure '7, each of these trains comprises ja series of clamped trains 60 of high frequency oscillation. Each damped train 60 of high frequency oscillation is'started by the closure of the buzzer contacts and the interval between the starting of successive train Bil is governed by the vibration period of the buzzer armature. The period of the high frequency oscillation is determined by the capacity of the condenser and the constants of the Tesla coil windings 26 and 25; it is usually 100,000 cycles or more per second. The starting effect of each train of impulses is-.proportional to the "amplitude of the high frequency oscillation and, is, therefore, at its maximum at the center of eachtrain.

In accordance with prior practices,-the spark coil leads" and 3| would merely be shunted across the alternating current mains 2| supplying current to the primary winding 20 of the transformer l8.

- In accordance with the present invention, however, the spark coil leads are not connected directly. across the mains 2| but across a resistance 82 which, in turn, is connected in series with a condenser (across the mains 2|; The operatidn of the conventional circuit and my preferred =circuit described, will now be explained in connection with the vector diagram shown in Figure 3 and the curvsof Figure 4.

-Referring to Figuresl and 3, the phase'of the p tential across the mains 2|, which is the potential applied to primary winding 20, is reprev sented by the vector N--'|.

I Under open circuit conditions, the potential developed in the secondary winding l9 will be substantially in phase with the potential applied to the primary wind-p ing; the open circuit secondary potential is therefore-represented by the vector N2 which extends in the same direction as vector Nl.

magnitudes are not shown in Figure 3.

The transformer I8 is preferably designed, as are most neon tube transformerato have a rel- I proximately equal in value to the total resistance of the secondary winding and the tube. Therefore, under operating conditions, the potential developed by the secondary winding 9 will comprise a resistance-component represented by the vector NIl and a reactance component represented by the vector 3'2. Of the resistance component N3, N represents the voltage drop in the tube and 4-3 the-voltage drop due to the resistance of the transformer. It will be observed that the potential across the tube represented by the vector. N-4 lags the potential NL impedance characteristic of such tubes the curveof the actual potential thereacross is very irregular. However, it is convenient in studying circuits of the type herein disclosed to represent the acitual wave by that sinewave which is most nearly equivalent in phase and amplitude to the actual wave. Curve 35 (Fig. 4) is this equivalent sine wave, and its phase is represented approximately correctly by vector N4 in Fig 3. -Wherever reference is made in the specification and claims to operating potential across the tube, or to the potential across the tube when the tube is operating, hi ls to beunderstood I am referring to the sine wave equivalent of the actual potential across the tube.

Referring'now to the starting circuit in Fig. 1, comprising the spark coil, 22, I have discovered by experiment that thepotential-impressed across such a coil (the potential across the leads 29 and 3i) when the buzzer is vibrating is consumed mainly by the resistance of the device and the and relative magnitude are indicated approximately correctly by the dotted vector NI.

The component of the applied voltage consumed in the reactance of the spark coil, is therefore represented by the dotted vector displaced from the dotted vector NI.

I havediscovered that the intensity or ampli- "tude of the high frequency discharge produced by the secondary winding 25 of the spark coil 22 is a periodically variable quantity passing through its maximum andminimum values substantially 'in a manner equivalent to being in phase with .of the potential applied to. the spark coil.

the reactance component (dotted vector Furthermore, the tube starting ability of the spark coil at any instant is measured by the intensity or amplitude o'f'the reactance component of the potential applied to the spark cell at that instant. Therefore the time of occurrence of the starting efiect produced on the tube I5 by the spark coil relative to the time of dccurrence ofoperatingpotential between the tube electrodes I6, is appronimately indicated by the phase displacement atively high leakage reactance for regulation purposes. This leakage reactance is usually apbetween the vectors Nl and 'I-fll. I

It will be observed from Figure 3 that vector leads vector Nl by wrangle-slightly in excess ,of 90; In other wordsjreferring to Figure 4, the high frequency-starting impulses represented by thedo'tted curves occur substantially at a,oas,sss is time when the operating potential across the at a time when the'operating potential represented by curve 33 is of amplitude suflicient to sustain a discharge in the tube. As has been previously stated, to be most effective, the starting ly thereto. A suitable phase-shifting circuit com impulses should reach maximum amplitude at the same instant as-the normal operating tube ptentiai, the vlatter being. in the process of being established as the tube begins to light and having to be successfully established if thetube is to remainiig'hted. 1

Inv accordance with the present invention, I connect the input circuit (leads\23 and 3|) of the spark coil 22.to the mains 2| through aphaseshifting .circuit instead of connecting them directprises a condenser 33 and a resistance 32 connected inseries across the mains H with the input terminals of the spark coil 22 shunted across the resistance 32, the circuit connection referred potential represented by curve35 attains its maxto being shown in Figure l.

, Referring now to the vector diagram of Figure 3, the potential applied to the condenser 33 and resistance 32 in series is the potential of the mains 2i and, as has been previously indicated, is represented by vector N-i This potential represented by vector N-i is the vector sum of the potentials 1 across resistance 32 and condenser 33, respectively. The potential across condenser 33 is determined by the reactance of the condenser and the current flowing therethrough. The potential ance, and it' has been found that by suitably proportioning the condenser 33, and the resistance 32 relative to the input impedance of the spark coll 22, the potential across the spark coil and resistance 32 can be made to lead the potential of the mains 2| and therefore to lead the tube operating potential by an amount greater than that which would obtain if the leads 2! and 3i were connected directly across the main 2i Therefore the potential across resistance 32 may be repre- .sented by vector N-3 and the potential across condenser 33 by vector 3 l.

Varying the valuefof condenser 33 and resistance 32 varies the relative lengths of vectors N- 5 and 3--l"and by properly choosing the condenser and resistance the potential represented by vector N-U may be made equal to that required by 'the, particular spark coil used. The vector diagram of Fig. 3 is approximately correct for a '65 system actually tested and is sumcientl'y accucomponent of the potential N-ii consumed by the resistance of the spark coil may be represented by the vector N6 and the component consumed in the reactance of the spark coil by the vector 3-3. It was previously pointed out that the tube terminals i6.

It will be apparent that since the operating potential applied to the electrodes it of tube l3 reaches a maximum value twice. during each cycle and that since the starting impulses applied to the tube I! over the electrode 28 also occur twice during each cycle, it makes no difference, in so far as their starting efiect is concerned, whether the starting impulses are in phase with the operating potentialacross the electrodes H3 or 180 but of phase therewith.

Thus, referring to Figure 4, 'the high frequency discharges; represented by curve 33,- which is drawn in the same phase relation to curve 35 as vector 3 -5 bears to vector N 4 Figure 3, occur substantially at the times when the operating imum amplitude.

It may be mentioned that although the currents flowing in the tube l5 and in the spark coil' circuit are not strictly sine-wave in shape (vector diagrams apply to sine-wave functions) and although the resistance of a hot cathode discharge tube of the type described is far from being a pure resistance, the use of vector diagrams do actually result in deductions in very close agree- I quite close to those therein shown. The variation seldom exceeds a few degrees and does not vary enough to alter the effectiveness of the phase shifting circuit described.

In the embodiment of the invention described in connection with Figure l, the terminals of the phase shifting circuit comprising condenser 33 and resistance 32are shown connected directly across the same ll0-volt lighting mains from which the primary winding 20 ofthe transformer l8 isenergized. By properly designing the spark coil 22 it can be made to deliver the necessary high potential impulses on the reduced voltage available across the resistance. 32. However, standard spark coils of the type used are designed for operation from 1l0-volt circuits and where a three-wire 220- volt oircuitis available, it is desirable to connect the 'condenser 33 and resistance 32 across 'the 220-yolt circuit as shown in Figure 2, the primary winding 20 of the transformer l8 being connect d between one side of the 220-vo1t main and Since in athree-wire 220-volt circuit the potential across the llo-volt-mains is in phase with the potentialacross the m-volt mains, the operation of the circuit-modifled as shown in Figure 2 is identical with that of the circuit shown in Figure l, except that theipotential applied to 'the spark coil is greater. i

It is practicable, when using the circuit .of Figthe spark coil more nearly 180 out of phase with the operating potential (vector N-4) across the tube. This result is of course to be desired.

Where a. poiyphase power circuit is available, approximately the desired phase shift between the potentials applied to the power transformer and the spark coil may be obtained by connecting them to different phases of 'the'circuit. Thus I have shown, in Figure 5, a gaseous discharge tube circuit similar to that of Figure 1, but energized from a three-phasesource. In Figure ,all of the elements corresponding to those in Figure 1 bear the same reference numeral with the suflix a. Thus the primary winding 20a of the transformer We is connected across one leg 39 of the secondary of a three-phase star connected transformer 81, the primary winding of which is not shown, and the conductors 29a and 3la leading from the spark coil 2211 are connected across one of the other legs 41 of the three-phase transformer secondary 31.

Referring to Figure 6, which, is a vector diagram illustrating the operation of the circuit shown in Figure 5, the vector N'38 represents the potential developed in the leg 39 of the threephase winding 31 and the vector N' 30 represents the relative phase of the potential developed in theleg M connected to the spark coil 22a.

As previously described in connection with Figure 3, the operating potential across the tube terminals l6a lags the potential applied to the primary winding 20a of transformer I8a and may be represented by the vector N'--48. Likewise the potential effective in the spark coil 22a, for developing the starting tendency, leads the potential developed in winding 4| and may be represented by the vector 4243, bearing the same relation to vector N40 as vector 56 to vector N-5 in Figure 3. It will be observed from an inspection of Figure 6 that as a result of the 120 1 displacement between the vectors .N--38 and N'4ll, the vector 42-43 is approximately parallel to the vector N'44. Therefore the starting impulses applied to the starting electrode Illa will be substantially in phase with the operating potential between electrodes Ilia, and will be fully effective for starting the tube.

Obviously several different tubes may be operated from different legs of the same poiyphase circuit, the starting coil associated with each tube being connected to a different phase than is the operating transformer associated with that tube.

Having fully described the preferred embodiment of this invention, it is to be understood that I do not limit myself to 'the exact construction herein set forth, which may obviously be varied in detail without departing from the spirit of this invention, butonly as set forth in the appended claims.

I claim:

1. In combination, a gaseous discharge tube, a source. of alternating current, and means for applying a potential derived from said source to said tube, said meanssupplying a potential to said tube suflicient to maintain the tube in operation but insuflicient to positively start the tube unaided and having substantial inductive reactance effectively in series with said source and tube,

whereby the potential across said tube, when the tube is operating, lags the potential of said source, means for starting said tube adapted to be energized from alternating current to produce a starting effect during a portion only of each half cycle of the energizing alternating current and phase-shifting means connecting said starting to sustain said tube in operation.

2. In combination, a gaseous discharge tube, a source of alternating current, and means for applying a potential derived from said source to said tube, said means supplying a potential to said tube suiilcient to maintain the tube in operation but insufficient to positively start the tube unaided and having substantial inductive reactance effectively in series with said source and tube, whereby the potential across said tube, when the tube is operating, lags the potential of said source, starting means for initially ionizing said tube comprising a spark coil energized from said source of alternating current, and phase-shifting means connected between said source and said spark coil for causing the potential applied to said spark coil to differ substantially in phase from the potential of said source.

3. In combination, a gaseous discharge tube, a source of alternating current, and means for applying a potential derived from said source to ,said tube,'said means supplying'a potential to said tube sufilcient to maintain the tube in operation but insufficient to positively start the tube unaided and having substantial inductive reactance effectively in series with said source and tube, whereby the potential across said tube, when the tube is operating, lags the potential of said source, starting means for initially ionizing said tube comprising a spark coilenergizedv from said source of alternating current, and phaseshifting' means connected between said source and said spark coil to cause the potentialapplied to said-spark coil to lead, in phase, the potential of said source.

4. In combination, a gaseous discharge tube,

a source of alternating current, and means for applying a potential derived from said source'to said tube, said means supplying a potential to said tube s-uflicie'nt to maintain the tube in operation but insuflicient to positively start the tube unaided and having substantial inductive reactance effectively in series 'with said source and tube, whereby the potential across said tube, when the tube'is operating, lags the potential of said source, starting means for initially ionizing the gas in said tube comprising a spark coiland a second source of alternating current of the same frequency but displaced approximately from 90 to'.120 in phase from said first source for energizing said spark coil.

5. In combination, a gaseous discharge tube, a

source of poiyphase alternating current, means another phase oi said source of alternating cursubstantial inductive reactance eii'ectively inseries with said source whereby the normal operating potential across said tube lags the potential of said source, starting means for ini- A tially ionizing said tube comprising a spark coil, and a condenser and a resistance connected in series across said source of alternating current, said spark coil being shunted across said resistance whereby the potential applied thereto leads A when, if the tube were operating, the potential the potential of said source. v

7. In combination with an alternating current supply system supplying high potential substantially double the low potential; a gaseous discharge lamp comprising a discharge tube and means energized from the low I potential leads of said source for supplying a potential to said tube suflloient to maintain the tube in operation but insuflicient to positively start the tube unaided and having substantial inductive reaetance effectively in series with said source and tube whereby the potential across said tube, when the tube is operating, lags the potential of said source; starting means for initially ionizing said tube comprising a spark coil adapted to normally operate on apotential equal to the low potential of said source; and phase-shifting means connected to the high potential leads of a low potential and a said source for supplying potential approximately equal in magnitude to said low potential, but ditiering in phase therefrom, to said spark coil.

8. In combination, an electric circuit, a gaseous discharge tube in said circuit, a gas in said tube, 5

a source of -a. c. power, means for applying a potential from said source to said circuit 0t masnitude sui'iicient to maintain said tube in operation but insumcient to start the tube unaided, inductive reactance in said circuit, separate means 10 to ionize the gas in said tube, and means for energizing said ionizing means in such phase relation with respect to the potential applied to said circuit and to the magnitude of said inductive reactance as to ionize the gas in said tube at a time 15 across the tube would be substantially at maxium amplitude.

9. In combination, an electric circuit, a gaseous discharge tube in said circuit, a gas in said :0 tube, a source of a. c. power, means for applying a potential from-said source. to said circuit of magnitude suflicient to maintain said tube in operation but insufllcient to start the tube unaided, inductive reactance in said circuit, separate means 25 energized from said source to ionize the gas in said tube, and means for applying current from said source to said ionizing means in such phase relation as to energize the latter at times when, it the tube were operating, the potential across the :0 tube would be substantially at maximum amphtude.

' arms 0. nmcxsou. 

